The present invention relates to a method for controlling flatness of a wafer and to a method of manufacturing a plurality of thin-film magnetic heads from a wafer by using the flatness control method.
When fabricating thin-film magnetic heads, performed are various wafer processes for forming many of arranged thin-film magnetic transducer elements on a wafer. Particularly, when fabricating composite or integrated thin-film magnetic heads each having a magnetoresistive effect (MR) transducer element currently in vogue and an inductive transducer element, since the structure is complicated for the improvement in characteristic, the wafer processes have become very complicated and new processes which were not experienced conventionally are necessary to perform. As a result, various and complicated stresses have affected the whole of the wafer.
According to the conventional technique, since it is difficult to compensate the influence of such complicated stresses, each wafer process may be performed under different flatness from each other.
However, if the improvement in a performance such as a record density is required much more from now on, these deteriorations in wafer flatness may cause variations in the depth of focus (DOF) in photo-processes or nonuniform polishing in chemical and mechanical polishing (CMP) processes. As a result, generation of inferior goods will increase and the yield will get worse.
It is therefore an object of the present invention to provide a method for controlling flatness of a wafer and to a manufacturing method of a thin-film magnetic head, whereby camber or warp of the wafer can be easily corrected during a wafer process.
According to the present invention, a method for controlling a flatness of a wafer with a warped concave surface, and a manufacturing method of a thin-film magnetic head includes a step of jet-spraying a gas at an extremely low temperature onto the warped concave surface of the wafer to correct the warped concave surface flat.
A gas at an extremely low temperature is jet-sprayed onto a warped concave surface of a wafer warped for any reason causing its flatness to deteriorate. Thus, the stresses on the front and back surfaces of the wafer are brought into balance so that the warp is corrected to improve the flatness of the wafer surface. Since a warp or distortion of the wafer can be easily corrected by jet-spraying an extremely low temperature gas, a flatness of the wafer can be easily controlled within a desired range in a short time during the wafer process. In complicated wafer processes, if this warp correction is repeatedly performed, it is possible to precisely complete each process. As a result, high performance thin-film magnetic heads can be fabricated with an excellent yield. Also, since the warp of the wafer can be corrected by jet-spraying a gas without contacting to the wafer surface, the flatness control can of a wafer surface be carried out even if elements are already formed on the wafer surface. Therefore, in a wafer process during which no flatness control has been possible to execute, a warp of a wafer can be corrected. Furthermore, the wafer surface will not deteriorate because only jet-spraying of gas is applied on the surface.
It is preferred that the gas contains particles made of the same material of that of the gas.
It is also preferred that the method further includes a step of jet-spraying an extremely low temperature gas for cleaning onto a surface opposite to the warped concave surface of the wafer, simultaneously with the step of jet-spraying a gas onto the warped concave surface.
It is preferred that the gas is a gas selected from CO2, He, Ar and N2 gases at an extremely low temperature.